There is an increasing interest in the nasal delivery of substances, typically pharmaceutical drugs, both as powders and liquids, for topical and systemic delivery.
Current delivery systems are not suited to the delivery of substances to the upper posterior region of the nasal airway, in particular targeted delivery to the olfactory region and the sinus ostia.
U.S. Pat. Nos. 4,013,075 and 4,889,114 disclose examples of prior art inhalation devices, which provide for the inhalation of a powdered substance from a capsule.
WO-A-00/051672, the content of which is herein incorporated by reference, discloses a delivery device for delivering a substance, in particular a medicament, in a bi-directional flow through the nasal cavities, that is, an air flow which passes into one nostril, around the posterior margin of the nasal septum and in the opposite direction out of the other nostril. A particular feature of this bi-directional mode of delivery is the ability to target defined regions in the nasal airway, for both topical and systemic delivery, in particular the upper posterior region which cannot be targeted with existing systems.
The present inventors have recognized that the delivery of powdered substances using the exhalation breath of a subject still presents a significant challenge, owing to the interaction of the moist exhaled air flow with the powdered substance prior to delivery into the nasal airway.
Exhalation into a device leads to condensation on the surfaces of the exposed device components, where the components are at a significantly lower temperature than the exhaled air flow, and significant condensation in the delivery channel will affect the consistency of the delivered doses.